Control system for paper-making machines



July 20, 1965 L. H. WlRTZ CONTROL SYSTEM FOR PAPER-MAKING MACHINES Filed June 12, 1962 2 Sheets-Sheet l INVENTOR LOUIS H. W|RTZ BY kvvn ATTORNEY 3;: x2 25:: A: 2:55: 2:: ..1 $32: $2552 2: 552 w Z 2:

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rllIill lll ll July 20, 1965 L. H. WIRTZ CONTROL SYSTEM FOR PAPER-MAKING MACHINES Filed June 12, 1962 2 Sheets-Sheet 2 FIG. 2

IIIZII United States Patent 3,196,372 (IQNTRQL SYSTEM FGR PAPER-MAKING MACHINES;

Louis H. Wirtz, ioughlreepsie, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed June 12, 1962, Ser. No. 262,011 11 Claims. (Cl. 152-198) The present invention relates to machinery and processes for manufacturing fibrous material, and more particularly to a measuring and controlling system for papermaking machines and the like.

In the manufacture of fibrous material such as textiles and paper it is useful to study the surface of the material to measure quantities such as fiber density, and it would be particularly useful to be able to study the surface of such materials during the manufacturing process so that evaluations may be made which could be immediately employed to control the manufacturing process. For example, in the paper-making art, one criterion for specifying finished paper products is by weight per unit area. Thus, by continually maintaining the surface fiber density of the paper at a given value, the weight per unit area, which is proportional thereto, may be controlled. Likewise, the quality of textiles, Whether woven from natural fibers such as cotton or artificial fibers such as rayon, is a measure of the fibers per unit length, or fiber density. By continually counting the fibers in the finished material, the weaving process could be controlled.

In devising a system for studying the surface structure of fibrous material, two important conditions must be satisfied. First, it is necessary that only the surface properties of the material be examined. Thus, a system wherein an optical device is located on one side of the material and a light source is directed through the material onto the optical device from the other side is not practical since it not only shows the structure of the surface, but also the structure of the secondary layers and opposite surface. Other systems are known which will examine only the surface of a material by having an optical device located above the material and a light source which di rects light onto the surface at an angle. The light reflect ed from the surface of the material is then received by the optical device. This method suffers the disadvantage that it only shows the shadows cast by the very high spots on the surface and does not show the minute structure of the surface. The first condition necessary in a system for studying the surface properties of fibrous material is that the system be able to examine only the surface of the material with a high degree of detail.

The other condition the system must satisfy is that it must operate as the material is being manufactured. This is necessary in order that corrections and variations may be made in the manufacturing process immediately after they are determined to be necessary by the examining device. This would require an examining device which operates on the material as it moves through the machine. For example, it may be possible to study surface properties by means of a highly sensitive stylus moved across the material surface, but this method would be impractical on the machine itself due to the motion of the material and the accompanying disturbances such as vibration, etc.

Accordingly, a system will be described wherein only the surface structure of a fibrous material is examined in detail, and which may be operated during the manufacture of the material as a control device. The invention will be depicted and described in relation to paper and a typical paper-making machine, but the principles of the invention are applicable to the manufacturing of fibrous materials in general.

An object of the present invention is to provide a systern for examining fibrous material and controlling the manufacture thereof.

Another o ject of the present invention is to provide a system for examining the surface structure of fibrous material.

A further object of the present invention is to provide a system for controlling the fiber density of fibrous material such as paper during the manufacturing process thereof.

A feature of the present invention is the provision of a system for controlling the fiber density of fibrous material during the manufacturing thereof including a device for producing a clear, transparent replica of the surface structure of the fibrous material, a scanning device for obtaining a count of the fibers per unit length of the fibrous material, a comparison device for comparing the obtained fiber count with a desired fiber count and for producing an error signal proportional to the difference between the counts, and a control device responsive to the error signal to adjust the manufacturing process of the fibrous material to provide the desired fiber count per unit length in the manufactured material.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a block diagram of a system for examining the surface structure of paper on a paper-making machine and controlling the machine accordingly;

FIG. 2 is a more detailed illustration of a unique de vice for measuring the surface characteristics of a fibrous material which is employed in the system of FIG. 1;

FIG. 3 is a sectional view of a photoelectric read head employed in the device shown in FIG. 2.

Referring to FIG. 1, the flow diagram for a typical Fourdrinier paper-making machine is shown including the refiner 1, the headbox 2, the Fourdrinier section 3, the presses 4, the dryers 5, the calenders 7, and the reel 8. In the present invention, a unique surface examining device 6 is provided, preferably located between the dryers 5 and the calenders 7. The output of the surface examining device 6 is connectced to a counter 9. Counter 9 is connected to a computing means 10 which is in turn connected to a control device 11. Control device 11 is connected to and adjusts the refiner 1.

The Fourdrinier paper-making machine is well known and has been widely used for paper manufacture for many years. A complete description of the Fourdrinier machine is available in the text Modern Pulp and Paper Making, Third Edition, John B. Calkin and George S. Witha'm, Sr., Reinhold Publishing Corporation, New York. There have been many changes and refinements made on the basic Fourdrinier machine since its introduction, but the basic component portions are illustrated in FIG. 1.

The first step in the paper-making process is the introduction of raw stock or pulp into the refiner 1.

Pulp as it comes from the pulp mill is generally not satisfactory for making most papers. The fibers are usually long and their surface characteristics such that they do not mat together to produce strong paper. Mechanical treatment is given the pulp to improve its felting properties. The mechanical treatment is termed refining and the device employed is referred to as a refiner. There are various types of refiners such as disc refiners and cone refiners. For purposes of this discussion the cone refiner will be considered, but the invention is applicable to any type refiner. The cone refiner consists of a cast iron, tapered shell fitted inside with blades running almost its full length. A conical plug fits into the shell which is also fitted with blades lengthwise on its surface.

3 V The plug revolves inside the shell and it may be moved back and forth so that the distance between the blades in the plug and those in the shell can be varied. Pulp is fed in the small end of the cone and removed'at the large end, being cut or brushed between the blades in the passage. The distance that the plug is located within the shell determines the degree of refining. 'Heretofore, this distance was adjusted manually, via a traversing gear and a hand wheel, but will be herein adjusted by a control device according to the principles of the present invention.

, The refined stock, after possibly being screened and chemically treated, is introduced into the headbox 2. The headbox is a large tank, the purpose of which is to take the aqueous fiber suspension from the refiner 1, spread it evenly across a wide area, and deliver it to the Fourdrinier section 3. The Fourdrinier section includes a horizontal wire screen onto which the refined stock from .the headbox 2 flows. form of an endless belt and travels constantly away from the point where the stock flows onto it. The water in the stock drains through the wire screen, being assisted by suction boxe under the screen. At the end of the wire 7 screen the stock still contains a large percentage of water,

and it is introduced into the presses 4, which include rollers which mechanically squeeze more water out of it. Next the stock is passed into the dryers 5, which include heated rollers which further remove water to the desired .point of dryness.

After leaving the dryers the sheet usually enters the calenders 7 which include smooth rollers which compress the sheet and give it .a smooth finish, after which it is wound on a reel 8.

'In the present invention a surface examining device 6 is provided between the dryers 5 and the calenders 7.

The function of surface examining device 6 to to examine only the surface of the sheet emerging from the dryers 5 and to determine the number of fibers per unit length of the sheet. The information from surface examining device 6 is transmitted to counter 9 which registers the fiber per unit length figure. The registered count is then transmitted to computing means 10, including signal source '10-1 and comparison means 10-2, which determines whether the count is proportioned to the desired density of finished paper which is being manufactured. If the count is not proportional, an error signal representative of the difference between the actual count and the desired count is generated and transmitted to control device 11.

Control device 11, in response to the value of the signal from comparison means 10-2 mechanically adjusts the plug of refiner 1 an appropriate distance with respect to the shell, thereby controlling the degree of refining. The degree of refining has a direct effect on the fibers per unit length, and consequently the density of the paper.

.This can be seen by considering the characteristics of the fibers. The cellulose fiber derived from wood has an outside, or primary wall, somewhat porous with crisscrossed fibers embedded in its inner surface but having a smooth,

slick outer surface. A secondary wall, being the main body of the fiber, has an outer layer consisting of hard twine windings in a close helix or spiral and an inner layer made of fuzzy, .soft twine windings in about ten or more windings of varying pitch.

Inside the inner portion of the secondary wall is the tertiary wall, which is similar to the primary wall except .that it has hard twine windings similar to those forming The wire screeen is made in the continuous sheet of matted fibers. The sheet of matted fibers, which is paper, has a finite thickness and upper and lower surfaces which lack smoothness, being composed of matted fibers.

As stated hereinabove, most methods for measuring the density of the paper require an examination of the entire sheet, including both surfaces and the interior portion. A simpler method would be to examine the surface of the sheet only and count the surface fibers per unit length of the sheet. This count will be directly proportional to the density, or weight per unit area of the paper.

As also discussed above, it is not possible to examine in detail only the surface of fibrous material with most known devices, particularly when it is desired to perform the examination during the manufacturing process.

Referring to FIG. 2, a more detailed illustration of surface examining device 6 is shown including a supply roller 6-1 containing a quantity of transparent deformable material 6-2. The transparent deformable material 6-2 is brought into contact with the upper surface of the paper sheet 12. The width of the transparent material 6-2 is much less than the width of the paper sheet 12, being in the order of one inch. The paper sheet 12 is emerging from dryer rollers 5-1, 5-2 and 5-3 which are included in the dryer stage 5 and is entering rollers 7-1 and 7-2 which are included in the calenders 7. After the transparent deformable material 6-2, which may for example be polyethylene film, leaves contact with the paper sheet 12 it is collected on take-up roller 6-3. Take-up roller 6-3 is driven by the same mechanism of the Fourdrinier machine (not shown) which drives the paper sheet 12 so that the transparent material 6-2 and the paper sheet 12 travel at the same speed. At the point where the transparent material 6-2 contacts the paper sheet 12 pressure is exerted by pressure rollers 6-4 and 6-5. The pressure exerted by rollers 6-4 and 6-5 cause the surface characteristics, that is, the fiber formation of the surface of paper sheet 12 to be impressed in the deformable surface of transparent material 6-2. Thus, a replica of the structure of the upper surface of paper sheet 12 is produced on the lower surface of transparent material 6-2 as it passes between rollers 6-4 and 6-5.

After leaving rollers 6-4 and 6-5 and before being wound on take-up roller 6-3 the transparent material 6-2 is passed through a read device 6-6 which includes a light sensitive device 6-7 disposed above the upper surface of transparent material 6-2 and a source of light 6-8 (preferably collim-ated light) disposed beneath the lower surface thereof such that the light from source 6-8 is directed perpendicularly through transparent material 6-2 onto light sensitive device 6-7 which is also disposed perpendicular to the material 6-2. The output of light sensitive device 6-7 is connected to counter 9 (FIG. 1) via lead 6-9. Light sensitive device 6-7 may, for example, be a photoelectric read head containing a photoelectric cell. 7 a

As the transparent material 6-2 passes light source 6-8 the light would normally be transmitted through without anyvariations since the material is clear and transparent, but since the lower surface contains depressions corresponding to the fibers on the upper surface of paper sheet 12, the light from source 6-8 is varied by these depressions, causing shadows in the same quantity, location and pattern as the fiber-s on the upper surface of paper sheet The light sensitive device 6-7, which receives the light passing through transparent material 6-2, is stationary.

' serve as light sensitive device is shown including a lens.

6-70, a screen 6-715 having a narrow aperture 6-7c and a photoelectric cell 6-7d. Functionally, photoelectric read head device 6-7 is similar to the read heads employed in motion picture projectors to scan the sound track on film. The similarity is that both devices scan and read narrow lines disposed on a transparent surface. In FIG. 3 the illumination 6-7e from source 6-8 (FIG. 2) is directed through transparent material 6-2. Transparent material 6-2, which has depressions in the lower surface thereof, is shown in a section view taken through it width. The depsessions in the lower susface of transparent material 6-2 which correspond to the fiber structure of the upper surface of paper sheet 12 (FIG. 2) show up as dark lines. A given portion of illumination 6-7e falls on lens 6-7rz after passing through transparent material 5-2. Lens 6-7:: magnifies this portion and directs it onto opaque screen 6-712. Screen 6-7 b has an aperture or slit 6-70 therein of predetermined length and width which permits only a small area of the illumination from 6-7:: to pass through.

The length and width or" aperture 6-70 is dimensionally selected to be in the same order as the fiber width. This dimension will vary with the type of wood used to produce the pulp, but is on the average of approximately 28 microns. Ir" a wide variety of wood pulps are to be used on the paper-making machines, it may be desirable to provide and adjustable aperture in screen 6-7.5 so that the dimensions of the opening could be pre-set in accordance with the wood pulp being used at any time.

Photoelectric cell 6-7d employed in light sensitive device 6-? may be a typical, commercially available photoelectric tube, or alternatively, and suitable light sensitive such as an electron multiplier tube, bolometer, photolytic cell, selenium cell, or the like may be used. The criterion necessary for photoelectric cell 6-742 or its alternatives is that it be able to respond to the light variations transmitted through aperture 6-7c and produce signals corresponding thereto.

ln the foregoing description it was stated that the width of transparent material 6-2 was approximately one inch and that light sensitive device 6-7 was stationary. This arrangement will detect the fibers within a very narrow portion of the width or" paper sheet 12. This will be sufiicient to determine and control fiber density, however, an alternative arrangement is possible wherein transparent material 6-2 is made much wider, for example, as wide as paper sheet 12, and light sensitive device 6-7 i moved transversely across the width thereof. In such arrangement the surface structure of the entire width of paper sheet 12 is examined, providing a more precise determination of the fiber density. To accomplish this alternative, light sensitive device 6-7 may be mounted on a carriage which transports it across the width of transparent material 6-2. The carriage would be driven, through a differential, by the motive means of the Fourdrinier machine so that the speed of device 6-7 is a function of the speed of paper sheet 12 and transparent material 6-2.

Transparent material 6-2, preferably being polyethylene film, may alternatively be any transparent, non-adhesive material capable of being deformed and retaining the deformation when pressed against fibrous material. Many plastics would be suitable, and even wax paper would be adequate.

The variations in the light received by photoelectric cell 6-7d (FIG. 3) due to the fiber depressions on transparent material 6-8 causes corresponding variations in the current through cell 6-70. The varying current is transmitted via lead 6-9 to counter 9 (FIG. 1). Each decrease in current transmitted through lead 6-9 indicates the presence of a fiber. Counter 9 counts the current variations as transparent material 6-2 moves past light sensitive device 6-7. A count of fiber per unit length is desired, so counter 9 is reset after a selected length of material 5-2 passes a fixed point. The longer the selected length, the higher will be the count, but a length of two inches is suflicient to produce a fiber per unit length figure which is indicative of fiber density. The counter is read out and reset each time the paper sheet 12 and transparent material 6-2; have traveled a two inch interval. A read out and reset pulse which occurs at two inch intervals may be generated in a wide variety of ways. For example, roller 6-4 may be selected to have an outside circumference of ten inches so that for each complete revolution of roller 6-4, paper sheet 12 and transparent material 6-2 will travel ten inches. A rotary switch 6-10 is mounted on the shaft of roller 6-4 and contains five contacts equally spaced seventy-two degrees apart so that for each complete revolution of roller 6-4 five equally time-spaced pulses art generated. Thus, a pulse is generated by rotary switch 6-10 for each two inch interval that paper sheet 12 and transparent material 6-2 travel. These pulses are transmitted on lead 6-11 to read out and reset counter 9. The figure which accumulates to counter 9 between the pulses on lead 6-121. is the number of fibers per two inches. The number of fibers per every two inches will vary according to the density or weight per unit area of the paper being manufactured, but the figure will characteristically be in the thousands so it is perferable that counter 9, which may be either a digital or analog type, have a range from 0 to 999,999.

Paper machines are operated over a wide range of speed, so the paper sheet 12 may be leaving the dryers 5 at speeds from 200 feet per minute up to 2,000 feet per minute. Since a count is read out from counter 9 for every two inches of paper sheet, a count may be transmitted from counter 9 in intervals of 0.05 second down to intervals of 0.005 second.

Each count is transmitted from counter 9 to comparison means 10-2 of computing means Computing means it) also includes a signal source 10-1 which provides a predetermined signal proportional to the fiber per unit length figure for the weight per unit area or density desired of the paper being manufactured. Comparison means 10-2 receives the count signal from counter 9 which is the actual count of the fibers per unit length of the material being manufactured and then compares the actual figure with the desired figure determined by the signal from source 10-1 and obtains the difference, if any, to produce an error signal. if counter 9 is a digital counter, comparison means 10 may be a second digital counter pre-set at the desired count. The outputs from counter 9 and the pre-set counter are subtracted by comparison means 10-2, which may be a digital comparator. The output of the digital comparator may then be applied to a digital-to-analog converter (not shown) to obtain an analog error signal proportional to the difference between the actual count and the desired count.

it the count signal from counter 9 is analog, computing means signal source 10-1 would be a source of analog signal, for example, a potentiometer preset at a value proportional to the desired count. The error signal may then be obtained by having comparison means 10-2 be a different amplifier responsive to the signals from the potentiometer and counter 9.

The aforesaid operations required of computing means 10 may also be performed by most electronic computers having a storage means which would serve as signal source Til-ll and an arithmetic means which would serve as comparison means 10-2. Either a digital or analog type computer may be employed.

The error signal from comparison means 10-2 is transmitted to a control device it which adjusts refiner 1 a sufiicient amount to change the actual fiber count to equal the desired count, or to within acceptable proximity thereto. For example, if the error signal from comparison means 10-2 is analog, control device 11 may be a servornotor mechanically coupled to the traversing gear presout on the refiner 1. The analog signal will cause the servomotor to rotate the traversing gear (usually operated by a hand wheel), thereby varying the distance that the refiner plug is located within the shell and thus controlling the degree of refining (which is proportional to the fiber count). The actual fiber count is thereby adjusted in accordance with the desired fiber count to produce the desired weight per unit area of the paper.

If computing means it) is a digital type, a digital-toanalog converter (not shown) may be employed as previously stated to provide the analog signal to the servomotor (control device 11).

An advantage of the present invention in addition to the control feature is that transparent material 62, after being wound on take-up roller 6-3, provides a permanent record of the surface structure of the paper. Transparent material 6-2 may be later viewed or photographed through a microscope or other suitable magnifying device so that detailed studies and measurements of the length, Width, position, deformation, etc., of the fibers may be made, thus providing a valuable tool for paper research. From the foregoing discussion it is seen that a new and useful device has been devised for examining the surface structure of paper. The device is used during the manufacture of the paper and continually monitors and controls the desired weight per unit area of the finished paper.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A machine for fabricating fibrous material of the type wherein the fibrous material emerges from the machine as a moving sheet comprising, in combination:

means for refining raw material into fibers,

means for processing said fibers into a moving sheet of fabric material, means for obtaining a replica of the surface structure of said moving fibrous material being fabricated,

means for scanning said replica to produce said first signal representative of the number of surface fibers per unit length of said fibrous material,

computing means including a source of second signal representative of a predetermined number of surface fibers per unit length of material, said computing means being responsive to said first signal from said scanning means for producing a third signal representative of the difference between said first and second signals,

and control means coupled to said refining means, said control means being responsive to said third signal for adjusting the refining means to maintain the number of surface fibers per unit length of the material being fabricated approximately equal to said predetermined number.

2. A system according to claim 1 wherein said means for obtaining a replica of the surface structure of said moving fibrous material includes a sheet of transparent,

non-adhesive material, deformable under pressure and means to press said transparent, non-adhesive material against said moving fibrous material to produce, by deformation, a replica of the surface structure of said fibrous material on the surface of said transparent, non-adhesive material.

3. A system according to claim 2 wherein said transparent, non-adhesive material is polyethylene film.

4. A system according to claim 2 wherein said scanning means includes a source of light mounted adjacent to one side of said deformed transparent sheet for directing light perpendicularly therethrough,

and a light responsive means mounted adjacent to the other side of said deformed transparent sheet and re- 8 sponsive to the light passing therethrough to produce said first signal.

5. A system according to claim 4 wherein said light responsive means is a photoelectric cell.

6. A machine for fabricating fibrous material of the type wherein the fibrous material emerges as a continuously moving sheet comprising, in combination,

means for refining raw material into fibers,

means for processing said fibers into a moving sheet of fibrous material,

a supply roller and a rotating take-up roller,

a sheet of transparent, non-adhesive material deformable under pressure connected between said supply roller and said rotating take-up roller and moving proximate to the moving sheet of fibrous material,

a pair of pressure rollers located between said supply roller and said take-up roller, said pressure rollers mounted on opposite sides of said moving transparent material and said moving fibrous material for pressing said transparent and fibrous materials together to produce, by deformation, a replica of the surface fibers of said fibrous material on the surface of said moving transparent material,

a scanning means located between said pressure rollers and said take-up roller, said scanning means including a source of light mounted adjacent to one side of said deformed transparent sheet for directing light perpendicularly therethrough, said light being interrupted by the depressions therein, and a light responsive means mounted adjacent to the other side of said deformed transparent sheet, responsive to the light passing therethrough to produce a signal representative of the number of depressions therein,

counting means responsive to the signal from said light responsive means for producing a count signal equal to said number of depressions, said count signal being representative of the number of fibers per unit length of said fibrous sheet,

means, including a source of predetermined signal representative of the number of fibers per unit length desired in said fibrous sheet, responsive to the count signal from said counting means for comparing said count signal with a said predetermined signal and producing a signal representative of the difference between said predetermined signal and said count signal,

and control means coupled to said refining means, said control means being responsive to said difference signal from said comparison means for adjusting the refining means to maintain the number of surface fibers per unit length of the fibrous material approximately equal to said predetermined number.

'7. A paper-making machine for fabricating a continuous sheet of paper from raw pulp comprising, in combination,

a refiner for refining raw pulp into fibers,

means for processing said fibers into a continuously moving sheet of paper,

means for obtaining a replica of the surface structure of the paper being fabricated,

means for optically scanning said replica to produce a signal representative of the number of surface fibers per unit length of said paper being fabricated,

means for producing a signal representative of a predetermined number of surface fibers per unit length desired of said paper being fabricated,

means responsive to said signals from said scanning means and said producing means for providing an error signal representative of the difference between said signals,

control means connected to the refiner and responsive to said error signal for adjusting the refiner to maintain the surface fibers per unit length of the paper being fabricated approximately equal to said predetermined number.

8. A system according to claim 7 wherein said means for obtaining a replica includes a supply roller and a rotat ing take-up roller,

a sheet of transparent, non-adhesive material, deformable under pressure, connected between said supply roller and said rotating take-up roller and moving proximate to the paper being fabricated,

and first and second pressure rollers located on opposite sides of said moving transparent sheet and moving paper for pressing said transparent sheet and paper together to produce, by deformation, a replica of the surface fibers of the paper on the surface of said transparent sheet.

9. A system according to claim 8 wherein said scanning means includes a source of light mounted adjacent to one side of said deformed transparent sheet between said pressure rollers and said take-up roller for directing light perpendicularly through said moving transparent sheet, said light being interrupted by the depressions in said transparent sheet,

a photoelectric device mounted adjacent to said moving transparent sheet on the side opposite said light source, said photoelectric device responsive to the light passing through a predetermined area of said transparent sheet to produce a signal representative of the number of depressions therein,

and an electronic counter responsive to the signal from said photoelectric cell for producing a count signal representative of the number of depressions in said transparent sheet.

19. A system according to claim 9 wherein said refiner includes a traversing gear for adjusting the degree of refining and wherein said control means includes a servomotor connected to said traversing gear for controlling the degree of refining in response to said error signal.

11. A method of fabricating a sheet of fibrous material having a predetermined number of surface fibers per unit length comprising the steps of,

refining raw material into fibers, processing said fibers into a fabric sheet, pressing a deformable sheet of material onto the surface of said fabric sheet to produce deformations due to the surface structure of the fabric sheet, counting said deformations over a given length of said deformable sheet, comparing said count with a predetermined number, obtaining the difference between said count and said predetermined figure, and adjusting said refining step in accordance with the 'itference between said count and said predetermined nurnber to produce said predetermined number of fibers per unit length in the surface of said fabric sheet.

References Cited by the Examiner UNITED STATES PATENTS 1,876,563 9/32 Buchner 162-198 1,971,296 8/34 Carpenter 162263 X 2,246,501 6/41 Bradner 162-498 X 2,806,373 9/57 Bendtsen 73159 2,963,397 12/60 McLeod 162198 3,624,484 3/62 Ziifer 162198 X 3,039,303 6/62 Reddick 73159 OTHER REFERENCES Drewsen: Paperboard Defects and Some Remedies, from PT], pp. 37, 38 and 39, March 26, 1942.

Montigny: The Rapid Measurement of an Index of Fiber Length, PTJ, vol. 123, No. 22, pp. 29-34, Nov. 28, 1946.

DONALL H. SYLVESTER, Primary Examiner. MORRIS O. WOLK, HOWARD R. CAINE, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,196,072 July 20, 1965 Louis Hc Wirtz It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below- Column 1, line 16, for "quantities" read qualities column 3, line 34, for "to", first occurrence, read is line 42, for "proportioned" read proportional column 5, line 11, for "susface" read surface line 65, for "variations" read variation same column 5, line 67, for "6-8" read 6-2 column 6, line 15, for "art" read are line 20, for "to" read in Signed and sealed this 22nd day of March 1966. 

1. A MACHINE FOR FABRICATING FIBROUS MATERIAL OF THE TYPE WHEREIN THE FIBROUS MATERIAL EMERGES FROM THE MACHINE AS A MOVING SHEET COMPRISING, IN COMBINATION: MEANS FOR REFINING RAW MATERIAL INTO FIBERS, MEANS FOR PROCESSING SAID FIBERS INTO A MOVING SHEET OF FABRIC MATERIAL, MEANS FOR OBTAINING A REPLICA OF THE SURFACE STRUCTURE OF SAID MOVING FIBROUS MATERIAL BEING FABRICATED, MEANS FOR SCANNING SAID REPLICA TO PRODUCE SAID FIRST SIGNAL REPRESENTATIVE TO THE NUMBER OF SURFACE FIBERS PER UNIT LENGTH OF SAID FIBROUS MATERIAL, COMPUTING MEANS INCLUDING A SOURCE OF SECOND SIGNAL REPRESENTATIVE OF A PREDETERMINED NUMBER OF SURFACE FIBERS PER UNIT LENGTH OF MATERIAL, SAID COMPUTING MEANS BEING RESPONSIVE TO SAID FIRST SIGNAL FROM SAID SCANNING MEANS FOR PRODUCING A THIRD SIGNAL REPRESENATATIVE OF THE DIFFERENCE BETWEEN SAID FIRST AND SECOND SIGNALS, AND CONTROL MEANS COUPLED TO SAID REFINING MEANS, SAID CONTROL MEANS BEING RESPONSIVE TO SAID THIRD SIGNAL FOR ADJUSTING THE REFINING MEANS TO MAINTAIN THE NUMBER OF SURFACE FIBERS PER UNIT LENGTH OF THE MATERIAL BEING FABRICATED APPROXIMATELY EQUAL TO SAID PREDETERMINED NUMBER.
 11. A METHOD OF FABRICATING A SHEET OF FIBROUS MATERIAL HAVING A PREDETERMINED NUMBER OF SURFACE FIBERS PER UNIT LENGTH COMPRISING THE STEPS OF, REFINING RAW MATERIAL INTO FIBERS, PROCESSING SAID FIBERS INTO A FABRIC SHEET, PRESSING A DEFORMABLE SHEET OF MATERIAL ONTO THE SURFACE OF SAID FABRIC SHEET TO PRODUCE DEFORMATIONS DUE TO THE SURFACE STRUCTURE OF THE FABRIC SHEET, COUNTING SAID DEFORMATION OVER A GIVEN LENGTH OF SAID DEFORMABLE SHEET, COMPARING SAID COUNT WITH A PREDETERMINED NUMBER, OBTAINING THE DIFFERENCE BETWEEN SAID COUNT AND SAID PREDETERMINED FIGURE, AND ADJUSTING SAID REFINING STEP IN ACCORDANCE WITH THE DIFFERENCE BETWEEN SAID COUNT AND SAID PREDETERMINED NUMBER TO PRODUCE SAID PREDETERMINED NUMBER OF FIBERS PER UNIT LENGTH IN THE SURFACE OF SAID FABRIC SHEET. 